City-Slicking Snakes? Road Loving Toads? Reptiles and Amphibians in Suburbia!
Increased urbanization, which may otherwise be known and defined as the conversion of natural ecosystems and landscapes into increasingly man-made, impervious surfaces (such as buildings, roadways, and pavement coverings), as well as into increasingly developed areas for human use, consumption, and/or habitation has been an increasingly prevalent factor contributing to many various conservation concerns, both directly and indirectly. Increased habitat loss and/or fragmentation, and even alteration, resulting in greater losses of our biodiversity, and drastic changes to species composition in our natural communities have been, and unfortunately continue to be major conservation challenges to overcome, for many of our plant, animal, and other forms of life throughout the world in which we reside and share with these thousands, if not millions of other species.
When it comes to their future fates, plants, animals, and all other forms of life must become adaptable in order to continue to survive and thrive, or otherwise perish. Change is an ever-present factor, and unfortunately, our (humans) increased growth and influence upon the environment have accelerated these rates of change at an increasing rate each year. With our actions, often comes changes or reductions in species composition, species biodiversity, reduction of natural food resources, competition and/or predation with new and domestic, or potentially invasive species, and increased environmental stressors and pollution, such as noise, air, and light pollution.
While some species have not been able to successfully adapt to these increased changes and pressures, and have thus perished or declined, others, in some cases, have been able to adapt while being afforded new ecological opportunities, lower predation and/or competition rates, and increased access to additional food and other resources. In some further cases yet, population densities in these urbanized areas may even exceed those of more rural or naturalized landscapes in which they may still occur.
When it comes to reptiles and amphibians, as a specific group of animals as a whole, much still remains to be investigated or studied into their tolerances or aversions, although further research and insight is becoming more readily available as we begin to better understand the ability of at least some of our scaly (or smooth skinned) neighbors to adapt to our ever-changing landscape. While we have previously examined many of the more generalized factors for influencing many of these animal’s distributions and habitat preferences in the article, “Where in the World?: Why Species Live Where They Do?”, this article examines some of the more specific potential factors pertaining to how or why some species can survive or even thrive in these greatly altered environments.
Generalist Natural Histories and Higher Adaptability
Perhaps one of the largest key factors when considering whether a species adapts or not to a new and changing urbanized environment relates to that given’ species’ existing natural history, or ready ability to quickly and effectively adapt. Species which tend to have broad and varied diets, temperature and humidity parameters, are habitat generalists as opposed to specialists, or other such successful attributes have the greatest likelihood of remaining common and widespread, even amongst our urban and suburban areas. When it comes to more highly specialized or sensitive species, unless such similar, and specific niches can be re-created or replicated in some other new and novel way, cannot usually be expected to thrive or adapt well to these types of landscapes. In the world of chelonians, painted turtles (Chrysemys picta) and Common snapping turtles (Chelydra serpentina), and haven two such species to be able to persist rather well in more degraded wetland environments, especially.
Through the many various human and manmade modifications in which we often tend to make, generalist species such as these have been able to locate and adapt quite well to the myriad of modifications these urban areas provide, whether they be natural or artificial ponds, lakes, ditches, or other wetland bodies, the introduction or co-establishment of more cosmopolitan food sources closely associated with mankind (such as an increased food supply of rats, mice, or small birds), our manmade waste products (such as trash, woods, metals, and other scrap debris which can provide both alternative cover habitat and food sources for many such reptiles, and amphibians, and the many other byproducts of our activities, which we afford these species their generalist needs, whether advertently or inadvertently.
Small Size and Ability, Crypsis, to Go Undetected
While certainly not always the case, many species of amphibians and reptiles which have been widely successful in being able to adapt to these environments oftentimes have the ability to better go undetected by much of the unobserving populace unless specific efforts are made to look for and appreciate them. This may be due to their small relative size as adults, and/or their coloration, patterning, or overall secretive nature, and the DeKay’s Brownsnake (Storeria dekayi), a generally small snake as adults which feed on worms, slugs, and other soft bodied insects or invertebrates, is one such example of a very common, “city slicking” snake which can often be found amongst our parks, gardens and backyards, or vacant lots. Likewise, eastern tiger salamanders (Ambystoma tigrinum), while might one expect most other salamander species to be readily and adversely affected by urbanization, have also been examples of species able to adapt to these climates due to their more fossorial and versatile nature amongst even farmsteads, open savannahs, and agricultural areas. As with all of these mentioned examples, such is often similarly the case for many other species found elsewhere throughout the world as well.
When it comes to snakes, especially, small size can often be beneficial in remaining undetected in the wake of persisting negative public perceptions of “large” snakes in closely populated urban areas. However, other species of snakes which have also adapted well to more urbanized environments often include the many various species of North American Ratsnakes (Pantherophis spp.), which are often the most commonly seen and encountered “large” snakes in metropolitan areas due to their generalist requirements, and fondness for eating substantial quantities of rodents and small birds. Similarly, even venomous species of snakes, such as the Eastern Copperhead (Agkistrodon contortrix), can persist in some urban areas due to this species’ excellent ability to remain cryptic amongst forest floor leaf litter and other debris.
High Fecundity/Reproductive Rate and Ability to Withstand Predators
A third attributing factor which can often suit a species well to an urbanized environment are their fecundity, or reproductive rates, as well as ability to potentially withstand new or novel predation from our associated domesticated species. Simply put, a species must be able to reach their sexual maturity and be able to produce and maintain relatively higher reproductive potential or output in order to be able to cope with these added and accelerated pressures upon their populations. Species such as many rattlesnakes (Crotalus spp.), for example, are quite slow to reach their sexual maturity, and also often produce relatively small broods of young, while possibly only reproducing every other year or even less frequently.
In contrast, some species of amphibians, such as our beloved and ubiquitous familiar American Toad (Anaxyrus americanus), or a similar replacement species, the Southern Toad (Anaxyrus terrestris) if one is located further southeast in the United States, are among the most adaptable and common amphibians to persist in urbanization, generally due to their more drier skins than many “frogs”, and ability to be explosive breeders during suitable environmental conditions, and are capable of producing as many as 20,000 eggs, within their jelly-like egg masses commonly known as “frogspawn”, where numerous, tiny “toadlets” can often be found hopping about upon sidewalks, on lawns, and just about any place else upon hatching from their water-sources.
Conclusion
In summary, reptiles and amphibians are among some of the most diverse and sometimes adaptable groups of animals on the planet, and many species have been able to form or establish new niches or are otherwise able to persist in our ever-changing global environment. Fortunately, or unfortunately, depending on how one chooses to perceive these animals, human encounters and other interactions with our native species of amphibians and reptiles, as well as many other plants and animals, have become an increasingly commonplace aspect as we continue to build and expand upon many of these animal’s natural landscapes, and which can sometimes lead to negative human-animal encounters or experiences with them as a whole.
Whether one likes them or not, there are ways everyone can learn to, at the least, better understand and appreciate these animals, their ecological purposes, and what we can do to be even more mindful of their presence, and our effects upon them, direct and indirect, good and bad, in ultimately being able to co-exist with them. In most, if not all cases of these animals being able to adapt to and thrive in suburbia, there is not only one of the above attributes leading to a given species’ success, but rather a combination, or multitude of different factors, some of which remain to be explored. This is, of course, not to say that our efforts to adjust our landscapes and alter our behaviors impacting them are always a complete substitute for conserving these animals in their more naturalized environments, but rather to simple acknowledge the growing realities of our impacts of human expansion globally while striving to do all but a small part of conserving these species locally and globally, while educating others about them.
Sources:
1. Petty, Micha R. Adapting to Suburbia. A Primer on Reptiles and Amphibians: A Collection of Educational Nature Bulletins. Louisiana Exotic Animal Resource Network. Elm Grove, LA. USA.
https://www.learnaboutcritters.org/files/herp-primer.pdf
2. Andrade, Antonio C. de. Metropolitan Lizards? Urbanization gradient and the density of largartixas (Tropidurus hispidus) in a tropical city. 30. Sept. 2019. Ecology and Evolution. Wiley Online Library. https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.5518